title: The orbitofrontal cortex as part of a hierarchical neural system mediating choice between two good options.
abstract: Animals rely on environmental cues to identify potential rewards and select the best reward available. The orbitofrontal cortex (OFC) is proposed to encode sensory-specific representations of expected outcome. However, its contribution to the selection of a preferred outcome among different reward options is still unclear. We investigated the effect of transient OFC inactivation (achieved by presession injection of muscimol and baclofen) in a novel two-reward choice task. In discrete trials, rats could choose between a solution of polycose and an equally caloric, but highly preferred, solution of sucrose by visiting one of two liquid dispensers after the presentation of a specific cue signaling the availability of one or both of the solutions. We found that OFC inactivation did not affect outcome preference: rats maintained high preference for sucrose and adapted their behavioral responding when the cue-outcome contingencies were reversed. However, when rats were tested drug-free 24 h after OFC inactivation and reversal learning, memory for the newly learned contingencies was poor. These results suggest a potential conflict between OFC (encoding pre-reversal contingencies) and other brain circuits (encoding the new contingencies). Remarkably, repeating the OFC inactivation before the reversal memory test restored normal behavior, confirming the hypothesis of a dominant impact of OFC on other decision-making circuits. These results indicate that the representations encoded in the OFC, while not essential to the expression of outcome preference, exert hierarchical control on downstream decision-making circuits.
authors.affiliation: Ernest Gallo Clinic and Research Center, Department of Neurology, Wheeler Center for the Neurobiology of Addiction, University of California at San Francisco, San Francisco, California 94143.
authors.forename: Ronald
authors.initials: R
authors.lastname: Keiflin
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Reese
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Woods
authors.forename: Patricia H
authors.initials: PH
authors.lastname: Janak
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D002755:Choice Behavior / Q000187:drug effects / Q000502:physiology*; D005625:Frontal Lobe / Q000187:drug effects / Q000502:physiology*; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists / Q000494:pharmacology; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012193:Reversal Learning / Q000187:drug effects / Q000502:physiology*; D012201:Reward
chemical_list: D058785:GABA-A Receptor Agonists; D058786:GABA-B Receptor Agonists; D009118:Muscimol; D001418:Baclofen